1. Field of the Invention
This invention relates to a single generally centrally mounted structure in a rear suspension system for a land vehicle, and more particularly to a weight transfer system for providing an adjustment between alternative riding conditions.
2. Discussion of Related Art
Rear suspension systems in land vehicles conventionally comprise apparatus which are mounted to the chassis of the vehicle in a plurality of locations. Typically, the rear suspension systems are heavy due to the number of components in the system, and the impact of the energy absorbed during the ride of the vehicle is absorbed by the driver.
Several rear suspension systems for snowmobile vehicles have been patented. For example, U.S. Pat. No. 4,826,260 to Plourde discloses a suspension system for an endless track vehicle, such as a snowmobile. The suspension system comprises a shock absorber unit being pivotally connected to a forwardly located crank arm, a strap and a retainer rod. The retainer rod extends across and is fixed to a front portion of a pair of lateral slides. The strap limits the downward movement of the front portion of the lateral slides by means of coil springs and a shock absorber unit. Furthermore, the shock absorber unit exerts a downward force on both the front and rear portions of the slides.
Another example of a rear suspension system for a snowmobile vehicle is U.S. Pat. No. 4,407,386 to Yasui et al. This patent discloses a suspension unit comprising a first shock absorber in a front portion of the rear suspension system, and a second shock absorber in a rear portion of the rear suspension system. The first shock absorber is connected to a proximal end of a guiderail by means of a cross tube, which is pivotally supported to the vehicle by means of bolts. The second shock absorber is connected to a distal end of the guiderail by means of bellcranks and arms. The bellcranks are pivotally supported on an axle which is journaled in the body of the snowmobile vehicle. Furthermore, the rear portion of the rear suspension system comprises a strap for limiting the maximum vertical travel of the guiderails with respect to the body of the vehicle at such time as the vehicle is vertically lifted off the ground. Accordingly, this patent limits the vertical lift of the guiderails by means of a two sets of shock absorber units, inc combination with springs, a strap, bellcranks and arms.
Other examples of patented rear suspension systems for land vehicles and snowmobiles include: U.S. Pat. No. 5,033,572 to Zulawski, U.S. Pat. No. 4,787,470 to Badsey, U.S. Pat. No. 4,546,842 to Yasui, U.S. Pat. No. 3,913,692 to Lohr et al, Japanese document 62-214065, and Japanese document 3-157283.
While each of the above described and cited rear suspension systems for land vehicles function adequately, they each have certain drawbacks. The major drawback is that the rear suspension systems are mounted to the underside of the chassis at both a front and rear portions thereof. The dual attachment of the prior art suspension systems in some circumstances add increased weight to the vehicle, reduce travel of the suspension, and increase the drag on a returning section of an endless track thereby decreasing the maximum speed achievable.
Therefore, what is desirable in a rear suspension system for a land vehicle is a generally centrally mounted rear suspension system capable of providing improved acceleration and cornering, an increase in the maximum speed achievable, a reduction in the weight of the vehicle by reducing the number of components in the suspension system, and an improved shock system for decreasing the workload of the components of the suspension system.